//Write a function that takes an unsigned integer and returns the number of '1' 
//bits it has (also known as the Hamming weight). 
//
// Note: 
//
// 
// Note that in some languages such as Java, there is no unsigned integer type. 
//In this case, the input will be given as a signed integer type. It should not af
//fect your implementation, as the integer's internal binary representation is the
// same, whether it is signed or unsigned. 
// In Java, the compiler represents the signed integers using 2's complement not
//ation. Therefore, in Example 3 above, the input represents the signed integer. -
//3. 
// 
//
// Follow up: If this function is called many times, how would you optimize it? 
//
//
// 
// Example 1: 
//
// 
//Input: n = 00000000000000000000000000001011
//Output: 3
//Explanation: The input binary string 00000000000000000000000000001011 has a to
//tal of three '1' bits.
// 
//
// Example 2: 
//
// 
//Input: n = 00000000000000000000000010000000
//Output: 1
//Explanation: The input binary string 00000000000000000000000010000000 has a to
//tal of one '1' bit.
// 
//
// Example 3: 
//
// 
//Input: n = 11111111111111111111111111111101
//Output: 31
//Explanation: The input binary string 11111111111111111111111111111101 has a to
//tal of thirty one '1' bits.
// 
//
// 
// Constraints: 
//
// 
// The input must be a binary string of length 32 
// 
// Related Topics 位运算 
// 👍 238 👎 0


//leetcode submit region begin(Prohibit modification and deletion)
public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        while(n != 0) {
            n &= n - 1;
            count++;
        }
        return count;
    }
}
//leetcode submit region end(Prohibit modification and deletion)
